Table of Contents - The Atmospheric Studies Group at TRC

Section 7: Prognostic Meteorological Interfaces
7.
PROGNOSTIC METEOROLOGICAL DATA PROCESSORS
Optionally, CALMET can accept prognostic data extracted from models such as MM5, Eta, RUC,
RAMS, WRF and TAPM and incorporate them in the computation of its own gridded meteorological
fields. Prognostic data for CALMET are typically prepared as a 3D.DAT file. Earlier formats for these
data are also supported: MM4.DAT and MM5.DAT, referring to the most likely origin of these earlier
data sets, i.e. the PSU/NCAR Mesoscale Modeling System 4 (MM4) or the PSU/NCAR Mesoscale
Modeling System 5 (MM5). However, not all modeling options in CALMET may be available if an
earlier file format is used. Interface programs that create the 3D.DAT files for CALMET from MM5, Eta,
RUC, RAMS and TAPM output products (CALMM5, CALETA, CALRUC, CALRAMS, CALWRF and
CALTAPM) are described in the following sections, followed by a description of the 3D.DAT file format
in Section 7.7.
7.1 CALMM5 Preprocessor
CALMM5 operates on the output from the PSU/NCAR Mesoscale Modeling System 5 (MM5), Version
3. It contains options to output the following MM5 variables: horizontal and vertical velocity
components, pressure, temperature, relative humidity, and water vapor, cloud, rain, snow, ice and graupel
mixing ratios (if available in MM5). Table 7-1 lists user-controlled options in CALMM5.INP.
The recommended format of the output file from CALMM5 for CALMET applications is the 3D.DAT
file format. Other output formats are available, including the old MM4.DAT format, but these are
intended for specialty uses. A 2D.DAT file may also be requested for surface variables (those without a
vertical profile). Table 7-2 lists the variables in 3D.DAT and MM4.DAT. Table 7-3 lists the variables in
2D.DAT files. Note that in 3D.DAT files, the five mixing ratios of cloud, rain, ice, snow, and graupel in
Table 7-2 can be zeros in most of profiles. To reduce file size in these cases, the zeros are compressed
using a negative value. For example, -5 means all five mixing ratios are zero.
CALMM5 reads and interprets all information contained in the MM5 header (physical options, dates, grid
size and location, etc.). Note that the MM5 header is read only once, for the first MM5 record in the MM5
file. MM5 grid specifications (latitude, longitude) are therefore saved at that time and assumed valid for
all subsequent times. This assumption fails if MM5 grid has moved during the MM5 simulation. The
output files from CALMM5 preserves some of the information of original MM5 configuration. In the
latest 3D.DAT/2D.DAT files (Data set Version 2.0), the header records have been modified to include
comment lines. These lines can be used to preserve detailed MM5 configurations in the further
development of CALMM5.
Data processing in CALMM5 is mainly due to the differences of coordinate systems between MM5 and
CALMET. In MM5, an Arakawa B-grid is used (Figure 7-1). There are two sets of horizontal grid
7-1